Is there anything about city life — besides a bad case of bedbugs — that makes grizzled New Yorkers scratch their heads? After quizzing friends, loved ones and colleagues, we found the answer to be a resounding “Yo!”

The city is full of puzzles: What’s that sticker in a subway car ceiling for? Is anyone ever actually ticketed for honking their horn? Where do hot dog vendors go to the bathroom?

Look no further! The Post went to the experts to get answers to these and other burning questions.

Have your own burning question about New York City? E-mail it to burning@nypost.com and we’ll get it answered in a future edition of The Post.

How much do beggars earn a day?

In a town where everyone is worried about climbing the social ladder, how much do folks on the lowest rung — panhandlers — rake in? The number depends on who you ask, but beggars queried by The Post said they can haul in anywhere from $20 to $200 a day. “More during holidays,” explained one Midtown hobo, who said he gets by on just $30 a day. Those with shticks do better. “Weed Head” — Jamaican-born Antonio Laird — dons a cardboard box festooned with pictures of marijuana and takes pictures with tourists; said kind buds pay him about $200 a day.

Is it illegal to kill a praying mantis?

Go to the playground and you’re bound to hear the same warning, repeated from generation to generation of New York kids — it’s illegal to kill a praying mantis. But is it true? No, says the state Department of Environmental Conservation. “This is an urban legend — but the praying mantis is very valuable in farming,” said spokesman Rodney Rivera. The critters were introduced to North America in the late 1800s to gobble garden pests, and lore around the legality of killing them is likely tied to how helpful they were. By the way, it’s not illegal to kill any insect in New York, the DEC said.

Do pedestrian walk boxes actually work?

Pedestrians have been pressing the button on the boxes that promises to turn the street light in their favor for years — and are still waiting for it to actually work. Don’t hold your breath. At most New York intersections, the “walk” message operates on a fixed-time mode. Pushing the button doesn’t change anything.

The DOT removes decommissioned pedestrian buttons when capital projects are scheduled for locations that include them, or when these intersections undergo other modifications, the agency said.

Citywide, there are only 100 active push-to-cross pedestrian buttons — in agency jargon, “actuated pedestrian signals.” These actually change to “walk” when someone pushes the button.

Can one out of seven Americans really “trace their roots to Kings County?

“Can we give a definitive number? No,” said John Paolo Canton, a spokesman for Ancestry.com, a genealogy Web site. Between 1892-1952 more than 12 million people immigrated to the US through Ellis Island — about 1⁄2 of the total US immigration. “How many settled in Brooklyn? We don’t know, but that’s a huge amount of people immigrating through the greater New York area.”

“There is no set number, especially with all the new immigration that has taken place not just in New York, but elsewhere,” added borough historian Ron Schweiger. “But it’s a substantial amount.”

What are the spray-painted markings on city streets and subway tunnels?

“They indicate where there is electrical, gas or steam equipment,” according to Con Ed spokesman Chris Olert. “If the city or a contractor is digging, they won’t hit our equipment and cause service interruptions — or get hurt.” After all, a jackhammer on a 13,000-volt cable is generally a bad thing. The paint — which fades over time — adheres to a nationally recognized color code: orange for communication/tv; red for electric; yellow for gas/oil/steam; green for sewer and drain; purple for unknown utility; and blue for water.

Why are there ominous-looking metal tanks on the sidewalk?

Don’t worry — they’re actually helping you reach out and touch someone! Verizon has an extensive program to pressurize its underground cables — pressurization keeps cables dry, but also alerts the company to a potential problem. In some instances, the company needs to add air to a particular cable or splice that may be vulnerable to water, moisture, humidity or steam. That’s when the nitrogen tanks — there are about 30 in Manhattan — come in, according to company spokesman John Bonomo. Verizon says they have never had a tank explode yet! “Nitrogen is about 70-80% of what we breathe anyway,” Bonomo said.

What’s that weird sticker on some subway car ceilings?

The stickers with thermometers are just that: They are where inspectors place laser thermometers to make sure temperatures in a subway cars fit within guidelines — between 58-78 degrees, depending on the season, MTA spokesman Kevin Ortiz said. They debuted in 2008, and it stuck.

Why has a ‘regular’ coffee come to mean ‘with milk and sugar?’

“I think it’s a part of New York jargon,” said Joseph DeRupo, a spokesman for the National Coffee Association. “My suspicion would lead me to believe that it originated with curbside carts, which are often run by immigrants who may have a language barrier. When customers say ‘regular’ maybe they took it to mean something else — or that’s how their coffee is drank in their country.”

What is the little red light on top of some street lamps?

It’s a beacon of light — atop another beacon of light. What are those little red lights on top of some city lampposts? It’s a fire alarm indicator lamp! “These are located on street lights mostly at intersections where there are fire alarm boxes to help indicate there is one nearby,” explained the Department of Transportation.

Since when did fortune cookies stop telling my fortune?

You’ve just scarfed down combination platter M14 and cracked open your fortune cookie — when you realize it’s not your lucky day at all with messages like “Put all your unhappiness aside, life is beautiful, be happy.” When did fortune cookies lose the fortune and start giving out life tips? Well, they’ve always had the tips, according to Derrick Wong, vice president for sales at Wonton Foods, a Brooklyn-based outfit that cranks out 4.5 million fortune cookies a day — the most in the country. It’s just that over the years, the number of tips and life lessons increased, thanks, he says, to consumer input. “It can’t be all fortunes 100 percent of the time,” he said. “Sometimes you want something funny, some philosophy — or a fortune telling.” But the most common recent request? “They say they prefer to see more fortune tellings,” Wong admitted. The pendulum may swing back.

Why doesn’t the MTA put MetroCard vending machines on the inside of the turnstile?

Ever notice that at precisely the moment you are refilling your MetroCard, your train will roll into the platform — now separated from you by two sets of stairs and a throng of harried commuters? Why doesn’t the MTA just put some vending machines inside the station?

Machines are placed outside fare control areas under the “simple premise that customers would need to purchase a MetroCard before entering the system,” explained MTA spokesman Kevin Ortiz, who said the agency has never experimented with installing machines inside. So maybe you just need to refill your card more quickly.

Do people actually get ticketed for horn honking?

They’ll never ticket me for honking my horn, right? Well, most of the time. Cops handed out 171 “unnecessary use of horn” summonses this year as of Oct. 30, according to Det. Cheryl Crispin. That’s a pittance compared to other infractions. In one year, for instance, the city issues about 10 million parking tickets. But still, if you really upset a police officer with your horn, it can be costly. It’s a $350 fine.

Why are trash trucks white?

Who wears white to play in the mud? City trash trucks! But why? “During the Lindsay administration, it was determined that the Department of Sanitation collection trucks would be white to reinforce that white would be more environmentally in step with the department’s mission of cleanliness,” explained spokeswoman Kathy Dawkins. There were brief flirtations with gray, then yellow, but white stuck.

How do fortune tellers afford such prime real estate when you never see any customers inside?

“It’s complex,” explained psychic medium Paul Advic. “They scare the people who do come into paying large sums of money to remove bad energy or demons. They are very good at reading faces.” Rents at the shops range from $150-$225 a square foot, according to Faith Hope Consolo of Prudential Douglas Elliman. “That’s a lot of palms,” she said. “They lure you in for a small amount and then they make significant money based on their individual reading or forecast. People feel vulnerable and give a lot of money, and they are flourishing now because there is so much uncertainty.”

Is it legal to hang a perpetual ‘Going Out of Business’ sign?

How can your favorite postcard/magnet/handbag/perfume store be going out of business — or at least claim that it is — for the last three years? It shouldn’t be. “If a business advertises that it’s having a ‘going out of business’ sale, it must have a special sale license from the Department of Consumer Affairs,” said agency spokeswoman Abigail Lootens. The license period cannot exceed 30 days — but the business can apply for one 30-day renewal. After that, Consumer Affairs can issue violations. But there’s the rub. A retailer can conceivable apply for a permit to go out of business every year, so long as no one complains about it. Report perpetual belly-under businesses to 311.

Is that music coming from my subway train?

Wondering why you’ve been humming show tunes while waiting for the train? Some subway trains — the R142 models that rumble along the 2,4, 5, 6 lines — are really alive with the sound of music. The three notes screeched out by the trains is a product of the model’s propulsion, which is generated in the train’s “truck” — the part that holds the wheels and carries the car body, according to the MTA. An eagle-eared Post reporter said the sound reminded him of “Somewhere Over the Rainbow,” but the MTA hears another tune. “Sounds more like ‘There’s A Place For Us’ from West Side Story to me,” said spokesman Adam Lisberg. But neither song exactly matches the R142’s tune, said Janice Yi, a Brooklyn photographer with perfect pitch. He pegs the train’s tones to a G, F and E, neither of which match “Rainbow” (A flat, A flat, A) or “Place” (A flat, F sharp, F).

Where do hot dog vendors go to go?

They are the men and women who fill New Yorkers’ bellies with delicious tubes of boiled meat — but where do hot dog vendors empty their bladders? “We go to area restaurants,” said one Midtown wiener slinger, who said a partner will mind his cart while nature calls. “You think we can take a leak and serve food? Not with the Health Department here every week. No BS!” It’s just a case of mind over matter. “Vendors must prepare mentally and physically to be outdoors for long periods of time,” noted Cesar Fuentes, executive director of the Food Vendors Committee of Red Hook Park, who added that vendors relish the chance to use fast-food restaurants, retail shops or public buildings with bathroom accessibility.

Why so many of those blue, Grecian-decorated coffee cups?

“That likely has to do with the predominance of Greek-owned diners in New York City,” Joseph DeRupo said. The “Anthora” designed cups with the “We are Happy to Serve You” slogan were first made by Connecticut-based Sherri Cup Company in 1963 — back when the majority of diners were Greek-owned. It sells over 15 million a month, according to the company’s Web site. That’s no joe-ke!